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Sump Caisson

Since the early 1970’s, sump caissons have been used in the oil and gas industry to contain and treat open and

closed drain streams, and accept produced water streams on offshore platforms. The segregrated drain and

produced water streams are directed to the caisson for controlled treatment and disposal.

The separation in the eProcess Sump Caisson typically occurs beneath the water surface in the engineered plated

section! and the treated water is discharged through the bottom of the caisson. The plated section! of the e"rocess

Sump #aisson consists of a series of internal baffles that create a coalescing $one and internal oil collection system,

which allows the oil droplets to be separated from the main flow regime and directed to the oil%water interface for

removal.

The most effective offshore treatment systems today segregate the open and closed drains from the produced water

stream. The open and closed drain streams are routed directly to the e"rocess Sump #aisson for treatment, while

the produced water system consisting of e"rocess &eoiler hydrocyclones, and &issolved 'as (lotation units are

routed separately to the e"rocess Sump #aisson for final disposal.

The e"rocess Sump #aisson has internal plates )baffles* with oil risers for the most efficient separation performance.

The e"rocess Sump #aisson is typically designed with a retention time of 10 + 0 minutes with a removal efficiency

ranging from -0100 microns pending on disposal re/uirements.

Open Drains

This wastewater stream is primarily from two sources, rainfall on the platform dec and wash down water. The

contaminates in this wastewater stream include oil, drilling mud and drill solids, spilled chemicals, worover fluids

and%or other byproducts of production operations.

The oil in this water is liely to be bul phase oil )crude or product* that has been partially dispersed in water. n the

case of wash down water, the stream could contain relatively high concentrations of soap. 2oth fine solids and soap

tend to stabili$e oil in water and mae it more difficult to separate.

Closed Drains

This waste stream is from a pressure source such as blow down of vessel bottoms. #ontaminants in the closed

drains might include oilwet solids, lubricating oils with heavy metals present and%or dispersed oil droplets. The waste

stream needs treatment and usually directed to the caisson. The e"rocess Sump #aisson includes an integrated

design to handle the contaminants from closed drains.

Solids Handling

n addition to effectively treating the open and closed drains of an offshore platform, the e"rocess Sump #aisson also

offers a degree of solids cleaning prior to disposal. 3s the solids flow down the internal baffles of the e"rocess Sump

#aisson, the abrasion caused by the closely spaced baffles allows free oil removal from the solids prior to disposal.

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Produced Water Disposal

4nce the produced water stream has been treated effectively in the upstream e"rocess system, the cleaned water

must be disposed. (or disposal on offshore platforms, an e"rocess Sump #aisson acts to prevent spills in the event

of an upset, or operational bypassing upstream if re/uired. n this case the e"rocess Sump #aisson provides

additional retention time and acts as a final holding vessel before disposal.

&isposal in this case is not considered a treatment step for the produced water stream5 therefore all disposal

regulations are met with the upstream produced water system.